The clock that directly causes ADC is call the Convert Clock in DAQmx. To change the ADC conversion rate you can use the DAQmx Timing Property Node located at All Functions >> NI Measurements >> DAQmx >> DAQmx Advanced >> DAQmx Constants and Property Nodes >> second row, third column. Then change the specific property by clicking the default property with the Operate Value tool (the pointing finger), select More >> AI Convert >> Rate.
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Micaela N
National Instruments